Issue #2246 - Implement Array find from last.

Based on the implementation from Mozilla bug 1704385.

2 files changed, 151 insertions, 0 deletions

diff --git a/js/src/builtin/Array.js b/js/src/builtin/Array.js
index 1e7776e228..f97e1df571 100644
--- a/js/src/builtin/Array.js
+++ b/js/src/builtin/Array.js
@@ -1210,6 +1210,72 @@ function ArrayAt(index) {
     return O[k];
 }
 
+// https://github.com/tc39/proposal-array-find-from-last
+// Array.prototype.findLast ( predicate, thisArg )
+function ArrayFindLast(predicate/*, thisArg*/) {
+    /* Steps 1. */
+    var O = ToObject(this);
+
+    /* Steps 2. */
+    var len = ToLength(O.length);
+
+    /* Step 3. */
+    if (arguments.length === 0) {
+        ThrowTypeError(JSMSG_MISSING_FUN_ARG, 0, "Array.prototype.findLast");
+    }
+    if (!IsCallable(predicate)) {
+        ThrowTypeError(JSMSG_NOT_FUNCTION, DecompileArg(0, predicate));
+    }
+
+    var T = arguments.length > 1 ? arguments[1] : undefined;
+
+    /* Step 4-5. */
+    for (var k = len - 1; k >= 0; k--) {
+        /* Steps 5.a-b. */
+        var kValue = O[k];
+        /* Steps 5.c-d. */
+        if (callContentFunction(predicate, T, kValue, k, O)) {
+            return kValue;
+        }
+    }
+
+    /* Step 6. */
+    return undefined;
+}
+
+// https://github.com/tc39/proposal-array-find-from-last
+// Array.prototype.findLastIndex ( predicate, thisArg )
+function ArrayFindLastIndex(predicate/*, thisArg*/) {
+    /* Steps 1. */
+    var O = ToObject(this);
+
+    /* Steps 2. */
+    var len = ToLength(O.length);
+
+    /* Step 3. */
+    if (arguments.length === 0) {
+        ThrowTypeError(JSMSG_MISSING_FUN_ARG, 0, "Array.prototype.findLastIndex");
+    }
+    if (!IsCallable(predicate)) {
+        ThrowTypeError(JSMSG_NOT_FUNCTION, DecompileArg(0, predicate));
+    }
+
+    var T = arguments.length > 1 ? arguments[1] : undefined;
+
+    /* Step 4-5. */
+    for (var k = len - 1; k >= 0; k--) {
+        /* Steps 5.a-b. */
+        var kValue = O[k];
+        /* Steps 5.c-d. */
+        if (callContentFunction(predicate, T, kValue, k, O)) {
+            return k;
+        }
+    }
+
+    /* Step 6. */
+    return -1;
+}
+
 function ArrayStaticConcat(arr, arg1) {
     if (arguments.length < 1)
         ThrowTypeError(JSMSG_MISSING_FUN_ARG, 0, 'Array.concat');
diff --git a/js/src/builtin/TypedArray.js b/js/src/builtin/TypedArray.js
index 5b7a1dfc22..22023aa7ca 100644
--- a/js/src/builtin/TypedArray.js
+++ b/js/src/builtin/TypedArray.js
@@ -1347,6 +1347,91 @@ function TypedArrayAt(index) {
     return obj[k];
 }
 
+// https://github.com/tc39/proposal-array-find-from-last
+// %TypedArray%.prototype.findLast ( predicate, thisArg )
+function TypedArrayFindLast(predicate/*, thisArg*/) {
+    // Step 1.
+    var O = this;
+
+    // Step 2.
+    var isTypedArray = IsTypedArrayEnsuringArrayBuffer(O);
+
+    // If we got here, `this` is either a typed array or a wrapper for one.
+
+    // Step 3.
+    var len;
+    if (isTypedArray) {
+        len = TypedArrayLength(O);
+    } else {
+        len = callFunction(CallTypedArrayMethodIfWrapped, O, "TypedArrayLengthMethod");
+    }
+
+    // Step 4.
+    if (arguments.length === 0) {
+        ThrowTypeError(JSMSG_MISSING_FUN_ARG, 0, "%TypedArray%.prototype.findLast");
+    }
+    if (!IsCallable(predicate)) {
+        ThrowTypeError(JSMSG_NOT_FUNCTION, DecompileArg(0, predicate));
+    }
+
+    var thisArg = arguments.length > 1 ? arguments[1] : void 0;
+
+    // Steps 5-6.
+    for (var k = len - 1; k >= 0; k--) {
+        // Steps 6.a-b.
+        var kValue = O[k];
+
+        // Steps 6.c-d.
+        if (callContentFunction(predicate, thisArg, kValue, k, O)) {
+            return kValue;
+        }
+    }
+
+    // Step 7.
+    return undefined;
+}
+
+// https://github.com/tc39/proposal-array-find-from-last
+// %TypedArray%.prototype.findLastIndex ( predicate, thisArg )
+function TypedArrayFindLastIndex(predicate/*, thisArg*/) {
+    // Step 1.
+    var O = this;
+
+    // Step 2.
+    var isTypedArray = IsTypedArrayEnsuringArrayBuffer(O);
+
+    // If we got here, `this` is either a typed array or a wrapper for one.
+
+    // Step 3.
+    var len;
+    if (isTypedArray) {
+        len = TypedArrayLength(O);
+    } else {
+        len = callFunction(CallTypedArrayMethodIfWrapped, O, "TypedArrayLengthMethod");
+    }
+
+    // Step 4.
+    if (arguments.length === 0) {
+        ThrowTypeError(JSMSG_MISSING_FUN_ARG, 0, "%TypedArray%.prototype.findLastIndex");
+    }
+    if (!IsCallable(predicate)) {
+        ThrowTypeError(JSMSG_NOT_FUNCTION, DecompileArg(0, predicate));
+    }
+
+    var thisArg = arguments.length > 1 ? arguments[1] : void 0;
+
+    // Steps 5-6.
+    for (var k = len - 1; k >= 0; k--) {
+        // Steps 6.a-f.
+        if (callContentFunction(predicate, thisArg, O[k], k, O)) {
+            return k;
+        }
+    }
+
+    // Step 7.
+    return -1;
+}
+
 // ES6 draft rev30 (2014/12/24) 22.2.3.30 %TypedArray%.prototype.values()
 function TypedArrayValues() {
     // Step 1.